Ozonation of Atactic Polypropylene

1963 ◽  
Vol 36 (2) ◽  
pp. 527-531 ◽  
Author(s):  
M. Lazar ◽  
I. Pavlinec ◽  
Z. Manasek ◽  
M. Micko ◽  
D. Berek
Keyword(s):  
Surface Layer ◽  
Room Temperature ◽  
Atactic Polypropylene ◽  
Simultaneous Formation ◽  
Kinetic Factor

Abstract 1. It is determined by study of the accumulation of peroxides in atactic polypropylene that ozone acts as an initiator of oxidation and considerably accelerates the course of the reaction even at room temperature. 2. The surface of the oxidized specimens is an important kinetic factor in the accumulation of the peroxides. 3. In addition to the formation of hydroperoxides in the initial phases of the process there takes place a crosslinking of the surface layer of the oxidized films by polymeric peroxides. These peroxides gradually decompose with the simultaneous formation of hydroperoxides. 4. The degradation of macromolecules under the action of ozone is less than in oxidation by the atmosphere.

Intercalation of pentane into the stage 2 to 4 cesium graphitides: Relation between cesium density in the intercalated layers and the stage of the parent binary

1993 ◽  
Vol 8 (9) ◽  
pp. 2288-2298 ◽  
Author(s):  
H. Pillière ◽  
M. Goldmann ◽  
F. Béguin
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Structural Transformations ◽  
Layer Model ◽  
Simultaneous Formation ◽  
Ternary Compounds ◽  
Second Stage ◽  
The Third ◽  
Cesium Ions ◽  
Third Stage

Isotherms (at 300 K and 328 K) and isobars (in the range 300 to 400 K) of n-pentane intercalation in CsC24 and CsC36 were established. With CsC24, three plateaus were identified at 0.52, 0.7, and 1.0 n-pentane/24 C, whereas only two plateaus at 0.8 and 0.97 n-pentane/36 C were found with CsC36. The progress of the reaction between n-pentane and CsC24, CsC36, and CsC56 (stage 2 to 4) was monitored by real-time neutron diffraction. The intercalation of n-pentane in CsC24 results in the simultaneous formation of a second stage ternary and a first stage binary “CsC8”, whereas, from the third stage CsC36 or the fourth stage CsC56, only pure second stage or third stage ternary compounds are formed, respectively. Owing to the formation of binary domains rich in alkali metal (CsC8) or to stage lowering produced by the ternarization, the in-plane cesium density is smaller in the ternary layer than in the starting binary. The electrostatic repulsion between the cesium ions, provoked by the sorption of n-pentane, is believed to be at the origin of the increased coverage. During the intercalation or de-intercalation processes, three-dimensional segregation occurs in each grain. A pleated layer model with canted fronts is presented. It accounts for the various phases present within each grain and for the structural transformations caused by pressure variations. At room temperature, the ternary layer seems to be disordered. The order-disorder transition appearing either by decreasing the temperature or by increasing the n-pentane pressure is correlated to a hindered motion of the intercalated molecules.

scholarly journals Room-temperature vacancy migration in crystalline Si from an ion-implanted surface layer

1999 ◽  
Vol 86 (9) ◽  
pp. 4861-4864 ◽  
Author(s):  
Arne Nylandsted Larsen ◽  
Carsten Christensen ◽  
Jon Wulff Petersen
Keyword(s):  
Surface Layer ◽  
Room Temperature ◽  
Vacancy Migration ◽  
Ion Implanted

scholarly journals Формирование преципитатов в Si, имплантированном ионами -=SUP=-64-=/SUP=-Zn-=SUP=-+-=/SUP=- и -=SUP=-16-=/SUP=-O-=SUP=-+-=/SUP=-

2018 ◽  
Vol 52 (8) ◽  
pp. 827
Author(s):  
В.В. Привезенцев ◽  
Е.П. Kириленко ◽  
А.В. Горячев ◽  
А.В. Лютцау
Keyword(s):  
Mass Spectrometry ◽  
Surface Layer ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Room Temperature ◽  
Secondary Ion Mass Spectrometry ◽  
Near Surface ◽  
Secondary Ion ◽  
Post Implantation ◽  
Scanning Electron

AbstractThe results of studying the surface Si layer and precipitate formation in CZ n -Si(100) samples sequentially implanted with ^64Zn^+ ions with a dose of 5 × 10^16 cm^2 and energy of 100 keV and ^16O^+ ions with the same dose but an energy of 33 keV at room temperature so that their projection paths R _ p = 70 nm would coincide are presented. The post-implantation samples are annealed for 1 h in an inert Ar medium in the temperature range of 400–900°C with a step of 100°C. The profiles of the implanted impurities are studied by time-of-flight secondary ion mass spectrometry. The Si surface is visualized using a scanning electron microscope, while the near-surface layer is visualized with the help of maps of elements formed by Auger electron spectroscopy with profiling over depth. The ZnO(002) texture is formed in an amorphized Si layer after the implantation of Zn and O ions. ZnO(102) crystallites of 5 nm in size are found in a recrystallized single-crystalline Si layer after annealing in Ar at 700°C.

scholarly journals Study of Helium Swelling in Nitride Ceramics at Different Irradiation Temperatures

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2415 ◽  
Author(s):  
Maxim. V. Zdorovets ◽  
Kanat Dukenbayev ◽  
Artem. L. Kozlovskiy
Keyword(s):  
Crystal Structure ◽  
Surface Layer ◽  
Room Temperature ◽  
Sharp Decrease ◽  
Radiation Doses ◽  
Near Surface ◽  
Helium Bubbles ◽  
Density Of Dislocations ◽  
Nitride Ceramics ◽  
Average Size

This paper presents the results of a systematic study of helium swelling and the subsequent process of degradation of the near-surface layer of aluminum-based nitride ceramics. The samples were irradiated with 40 keV He2+ ions at temperatures of 300 and 1000 K with a fluence of 1 × 1017–5 × 1017 ions/cm2. The choice of radiation doses and temperature conditions was due to the possibility of simulating reactor tests of structural materials. It has been established that an increase in the irradiation fluence leads to the formation of large agglomerates of clusters of helium bubbles, as well as an increase in the degree of roughness and waviness of the surface with the formation of crater-like inclusions. In the case of irradiation at high temperatures, there was a slight decrease in the average size of helium inclusions compared with irradiation at room temperature. However, the density of inclusions and surface roughness were much higher. It is established that irradiation at room temperatures leads to a sharp decrease in ceramics density, as well as deformation of the crystal structure due to an increase in the density of dislocations and macrostresses in the structure. The decrease in ceramics density due to the formation of helium inclusions led to an increase in porosity and a defective fraction in the structure of the surface layer of ceramics.

Erzeugung von freien Defektelektronen in 2,3 Dimethylnaphthalin- Einkristallen mit schwach absorbiertem Licht/ Photo generation of Holes in 2,3-Dimethylnaphthalene by Weakly Absorbed Light

1975 ◽  
Vol 30 (10) ◽  
pp. 1315-1327
Author(s):  
W.-W. Falter
Keyword(s):  
Surface Layer ◽  
Room Temperature ◽  
Second Harmonic ◽  
Incident Light ◽  
Crystal Defects ◽  
Recombination Coefficient ◽  
Nitrogen Laser ◽  
Light Pulses ◽  
Electronically Excited ◽  
Current Densities

Abstract Irradiation of 2,3 DN single crystals by 5 nsec light pulses from a nitrogen laser (337 nm) and by 20 nsec light pulses from a Q-switched ruby laser (347 nm, second harmonic) respectively, causes generation of free holes. Centers which are most probably associated with crystal defects are electronically excited by the incident light directly or by energy transfer from the primary excited 2,3 DN. The excited centers are quenched by charge transfer interaction with 2,3 DN. Mobile holes are separated from the localized negatively charged centers subject to the applied electric field. The centers are distributed uniformly over most of the volume, but in a region closer than 1 μm to the surface the concentration increases rapidly. In this surface layer also a high density of hole traps are found to exist, which are responsible for the temperature dependent rise of the photocurrent pulses below room temperature. At high current densities recombination between ionized centers and drifting holes becomes important. The recombination coefficient is found to be 10-5 cm3 /sec. Analysation of the fast (60 nsec) rise of the photocurrent pulses above room temperature gives information about the lifetime of the excited centers and about the lifetime of the singlet excitons in the surface layer. Values of ≈ 30 nsec for the centers and ≲ 10 nsec for the excitons are found. The volume lifetime of the singlet excitons is measured to be 80 nsec.

scholarly journals MODIFICATION OF A CHARGED-BOSE-GAS MODEL FOR OBSERVED ROOM-TEMPERATURE SUPERCONDUCTIVITY IN NARROW CHANNELS THROUGH FILMS OF OXIDIZED ATACTIC POLYPROPYLENE

2011 ◽  
Vol 25 (14) ◽  
pp. 1845-1875 ◽  
Author(s):  
D. M. EAGLES
Keyword(s):  
Room Temperature ◽  
Bose Condensation ◽  
Initial Slope ◽  
Atactic Polypropylene ◽  
Minimum Diameter ◽  
Narrow Channels ◽  
Minimum Number ◽  
The One ◽  
Walled Carbon Nanotubes ◽  
Room Temperature Superconductivity

Reasons have been found for thinking that the minimum diameter of channels of a given length to support superconductivity through films of oxidized atactic polypropylene (OAPP) at room temperature is considerably larger than that found in a model for Bose condensation in an array of nanofilaments [D. M. Eagles, Philos. Mag.85, 1931 (2005)] used previously. This model was introduced to interpret experimental results dating from 1988 on OAPP. The channels are thought to be of larger diameter than believed before because, for an N–S–N system where the superconductor consists of an array of single-walled carbon nanotubes, the resistance, for good contacts, is RQ/2N, where N is the number of nanotubes and RQ = 12.9 k Ω [see e.g., M. Ferrier et al., Solid State Commun.131, 615 (2004)]. We assume this would be 2RQ/N for a triplet superconductor with all spins in the same direction and no orbital degeneracy, which may be the case for nanofilaments in OAPP. Hence one may infer a minimum number of filaments for a given resistance. In the present model, the E(K) curve for the bosons is taken to be of a Bogoliubov form, but with a less steep initial linear term in the dispersion at Tc than the one at low T. This form is different from the simple linear plus quadratic dispersion, with a steeper initial slope, used in my 2005 paper. A combination of theory and experimental data has been used to find approximate constraints on parameters appearing in the theory.

Modified Bitumens Containing Thermoplastic Polymers

1980 ◽  
Vol 53 (4) ◽  
pp. 994-1005 ◽  
Author(s):  
S. Piazza ◽  
A. Arcozzi ◽  
C. Verga
Keyword(s):  
Block Copolymer ◽  
Low Temperature ◽  
Polymer Blends ◽  
Room Temperature ◽  
Viscoelastic Behaviour ◽  
Mixing Process ◽  
Atactic Polypropylene ◽  
Thermoplastic Polymers ◽  
Aromatic Content

Abstract The mechanical and viscoelastic behaviour of bitumen, both at high and low temperature, is noticeably improved by addition of thermoplastic polymers such as thermoplastic SBS rubbers and atactic polypropylene. These polymers can be used complementary to each other. Atactic polypropylene decreases the flow of bitumen at room temperature, thus reducing creep. The SBS block copolymer, instead, prevents excessive stiffening of bitumen at low temperature, reducing the brittleness. Characteristics of bitumen-polymer blends depend heavily upon bitumen quality, particularly upon its aromatic content and mixing process.

scholarly journals Microstructures of Three In-Situ Reinforcements and the Effect on the Tensile Strengths of an Al-Si-Cu-Mg-Ni Alloy

2018 ◽  
Vol 8 (9) ◽  
pp. 1523 ◽  
Author(s):  
Lusha Tian ◽  
Yongchun Guo ◽  
Jianping Li ◽  
Feng Xia ◽  
Minxian Liang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Simultaneous Formation ◽  
X Ray ◽  
Transmission Electron ◽  
Ni Alloy ◽  
Al3ti Phase ◽  
Scanning Electron

In the present paper, the microstructures of three kinds of in-situ reinforcements Al-Ti-C, Al-Ti-B, and Al-Ti-B-C-Ce were deeply investigated using a combination of scanning electron microscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. The effect of in-situ reinforcements on the room temperature and elevated temperature (350 °C) tensile strengths of Al-13Si-4Cu-1Mg-2Ni alloy were analyzed. It is found that doping with trace amounts of B and Ce, the size of the Al3Ti phase in the in-situ reinforced alloy changed from 80 µm (un-reinforced) to about 10 µm, with the simultaneous formation of the AlTiCe phase. The Al-Ti-B-C-Ce reinforcement which is rapid solidified, was more effective and superior to enhance the tensile strengths of the Al-13Si-4Cu-1Mg-2Ni alloy, both at room and high temperatures than those of addition other reinforcements. The room temperature (RT) strength increased by 19.0%, and the 350 °C-strength increased by 18.4%.

Ion-Irradiation Study of the “Exotic” Mineral Neptunite: LiNa2K(Fe,Mg,Mn)2Ti2Si8O24

1990 ◽  
Vol 201 ◽  
Author(s):  
Ray K. Eby ◽  
L. M. Wang ◽  
G. W. Arnold ◽  
R. C. Ewing
Keyword(s):  
Surface Layer ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Amorphous Layer ◽  
Narrow Region ◽  
Transmission Electron ◽  
Room Temperature Aging ◽  
Transparent Region ◽  
Amorphous Surface ◽  
Temperature Aging

AbstractSingle crystals of the silicate neptunite were irradiated with 600 keV Ar2+ and 1.5 MeV Kr+ and analysed by transmission electron microscopy. Amorphization was observed in a surface layer several hundred angstroms thick following Ar2+ irradiations up to 5.0×l013 Ar/cm2, yet the Ar2+ ions travelled an average of 1/2 μm in depth. The microstructure of the amorphous surface layer depends on the ion fluence, but the amorphous layer thickness remained constant. At the highest fluence, a narrow region below the amorphous layer shows a brittle-to-ductile strain transition, due to tensional volume-expansion of the adjacent ductile amorphous layer. With 1.5 MeV Kr1+, amorphization of the electron transparent region was completed after a fluence of 1.7×l014 Kr+/cm2, and no further damage was observed up to 5.1×1015 Kr+/cm2. However, following a low fluence of 2.0×1011 Kr+/cm2, a single crystal of neptunite became a polycrystalline aggregate (grain size 10 nm) within 7 days of room temperature aging.

Sign in / Sign up

Export Citation Format

Share Document